More neutral/ground bonding questions

[dmarkh]

I have an ST-10 driven by a Changfa 1115. It is semi portable, enclosed on a trailer. I am the second owner. The first owner considered it a portable because he used it mostly stand alone in remote locations. He did use it also to run his home when needed via his dryer port. It is configured as a portable with respect to neutral and ground. They are bonded in the fuse panel in the trailer enclosure.

Ok, me, the new owner still intends to use it occasionally in the same fashion. Except not nearly as often as he did. It will be mainly a backup generator for my home. In fact I just had a new breaker panel installed in the garage and upgraded to a 200 amp service which included a separate panel outside the garage where the mains is now located that includes one of those special generator transfer switches such that only one of the other can be physically switched to on. The generator will be located about 20 ft from that mains panel and I am running wires from the the panel under ground to a "junction box/panel" located in the area of the generator that will hold a cable/connector to connect to the generator when needed. I had a ground rod installed there also when the work was done.

I know in this configuration that I should have an un-bonded neutral and ground and I plan on changing it. Now my questions.

1. When I do take this thing "out" so to say, I really need neutral and ground bonded. I have an internal 15 amp 4 banger inside  the enclosure that is used to run little things like a battery charger, fans, etc. I've seen a special plug that can be pugged into that, that will bond neutral and ground. But I've also read "on the internet" that they are not recommended for those Chinese heads for some reason. Is there any truth to that?

2. For the normal house hookup, the panel outside the garage does not switch neutral/gnd. There were 2 new grounding rods installed near the panel when the work was done. They are 20 ft from the generator "hookup box".  Should I still run a gnd wire to the panel from the generator "junction box/panel", even though I will have the gnd wire and chassis connected to the grounding rod at the "junction box/panel"?

3. In it's current configuration there is no connection between the green ground wire and the generator chassis. I thought this connection would be done within the head its self. Can someone explain this?

Thanks
Mark

[BruceM]

http://www.doityourself.com/forum/electrical-ac-dc/492409-correctly-grounding-house-back-up-generator-multiple-sub-panels.html

Furd did a great job of simply explaining the proper hookup, and why, in the above link. 

Since your transfer switch doesn't switch the neutral, your earth connection must come from the main panel.  You should also check to make sure that all other panels are now properly configured as sub panels with NO Neutral to ground connection or shorts. 

If you want to use the generator as a stand alone power unit also, you should do it in a manner that does connect neutral and ground, but preferably in a manner which can't be left in place when operating as backup power.  A three phase transfer switch comes to mind-  one way for backup house feed, one way for stand alone. 

[dmarkh]

http://www.doityourself.com/forum/electrical-ac-dc/492409-correctly-grounding-house-back-up-generator-multiple-sub-panels.html

Furd did a great job of simply explaining the proper hookup, and why, in the above link. 

Since your transfer switch doesn't switch the neutral, your earth connection must come from the main panel.  You should also check to make sure that all other panels are now properly configured as sub panels with NO Neutral to ground connection or shorts. 

If you want to use the generator as a stand alone power unit also, you should do it in a manner that does connect neutral and ground, but preferably in a manner which can't be left in place when operating as backup power.  A three phase transfer switch comes to mind-  one way for backup house feed, one way for stand alone. 

Yes that was a good read. I understand now there is no way to do it correctly and to code unless I can switch neutral. I just got off the phone with my contractor and he assures me it will be a piece of cake to add in a real transfer switch that did switch neutral. So that is what I'm going to do. Just not this hurricane season. My wife is already on me regarding money spent. It will be done before the next one though. So in the mean time, my contractor said to go ahead and run my wires out to the generator leaving neutral and gnd bonded at the generator (like any off the shelf portable will have) and to go ahead and connect my floating chassis to the gnd rod. Not sure what that will get me but Ok.

Mark

[dmarkh]

Referring back to my OP,

Once I get my house right and neutral and gnd are no longer bonded in the generator:

When I do take this thing "out" so to say, I really need neutral and ground bonded. I have an internal 15 amp 4 banger inside  the enclosure that is used to run little things like a battery charger, fans, etc. I've seen a special plug that can be pugged into that, that will bond neutral and ground. But I've also read "on the internet" that they are not recommended for those Chinese heads for some reason.

Is there any truth to that?

Thanks
Mark

[BruceM]

Single point connection of the neutral and safety ground (at the main panel) is what you want.  There's nothing wrong or special with the ST heads in that regards. 

Your setup would be better if you just used the main panel's earth ground.   Adding another neutral to earth connection is a bad choice. It causes more neutral current to flow through the earth, more net neutral current at your home, and elevated magnetic fields.

You can add a ground rod to the extended safety ground from the main panel, without violating code.

If your connection from the generator was through a 4 wire plug, you could have another female socket connected to some outlets at the generator that could only be connected by unplugging the house plug. Then you can connect the Neutral and ground at the local outlet box.  A transfer switch (3 leg) or 3PDT contactor could also do the switchover at the generator.

[dmarkh]

OK, I think I'm less confused now after reading and reading and reading again all your inputs and links. Until I am able to switch neutral at the house I will go ahead and un-bond neutral at the generator. I just won't take it out in the field like that. In the end I will be able to switch neutral at the house and at that point I will bond neutral at the gen and be able to haul it to the field anytime I want.

I'm still unclear as to why the green gnd wire at the gen has no connection to the chassis. Should I connect the gen chassis to my unused grounding rod?

Thanks

[buickanddeere]

  Should not have a path that energizes the ground system with neutral current.
  Most people seem to think the neutral harmless ? It's an insulated current carrying power conductor just like Line 1, Line 2, Line 3 etc.  The neutral just happens to be near to earth's voltage potential.

[dmarkh]

OK, I have unbonded neutral and gnd in the generator breaker box located in the generator enclosure. I have bonded the chassis and trailer to gnd. I will not be using the grounding rod I had installed out where the thing sits. I will just be running the gnd to the house with the rest of the wires where there are 2 new grounding rods installed when the service was done recently.

Like I posted earlier, this mobile trailered generator will be sitting about 20 feet from the mains located on the outside wall of the garage. It will be used nowhere but from there for the next year or so. The mains has an interlock fitted with a 50 amp breaker for the gen. There is a 40 amp breaker in the generator enclosure. I intend to run 60 amp (under ground rated) wires ( I may get a bigger gen in the future?) in PVC under ground from the house to where the generator will live. So I've got to go down the outside wall from the mains, then underground for about 20 ft, then up. I see coming up through a mini concrete slab/block where I envision a metal pipe with some kind of weather proof box on it. In that box I see a 10 ft. cable wrapped up that I can just take out and connect to the generator when needed.

Am I seeing things? Is there anything wrong with what I want to do?

This "box" I see, is there a technical name for it? It would have nothing in it except the 10 ft of cable wrapped up and whatever hardware was required to join to the under ground cable from the mains to that 10 ft cable. I've been searching the net for a plano weather proof box/panel and haven't found anything. Lots of panels and boxes but they are all for something else.

Can I run PVC all the way to this box? Even down into the ground from the mains panel?

It's still gonna be a month or so before I start digging. I have to wait for my 8x10 carport that it's gonna live under to be delivered. Any ideas or recommendations are welcome.

Thanks
Mark

[BruceM]

" I intend to run 60 amp (under ground rated) wires ( I may get a bigger gen in the future?) in PVC under ground from the house to where the generator will live."

No need for direct burial wire/cable  in PVC conduit, do NOT use PVC jacketed cable with multi strands and ground in conduit (a no-no for thermal reasons). THWN individual wires would typically be used.

Terminating to a cable is a bad idea. I would terminate to a outdoor rated RV type power plug, in an outdoor rated box.  The conduit should be steel up into the box, get a Rigid conduit or IMC sweep .  Pipe tape wrap the steel where buried.  The pipe terminates in the box with a standard box termination (male thread) and box nut.

[dmarkh]

" I intend to run 60 amp (under ground rated) wires ( I may get a bigger gen in the future?) in PVC under ground from the house to where the generator will live."

No need for direct burial wire/cable  in PVC conduit, do NOT use PVC jacketed cable with multi strands and ground in conduit (a no-no for thermal reasons). THWN individual wires would typically be used.

Terminating to a cable is a bad idea. I would terminate to a outdoor rated RV type power plug, in an outdoor rated box.  The conduit should be steel up into the box, get a Rigid conduit or IMC sweep .  Pipe tape wrap the steel where buried.  The pipe terminates in the box with a standard box termination (male thread) and box nut.

Thanks for that.

I just got one of these for the generator and it looks like it will work well for the hookup end too.

Connecticut Electric CESMPS54HR 50-Amps/120240-Volt RV Power Outlet"

I have a real problem burying any amount of steel out there. I'm not familiar with pipe tape wrap but still. Is there rigid conduit with spme sort of welded plate on the bottom that could be bolted to the concrete and allow me to run the PVC up into it? As far as the connection at the mains, can I run PVC all the way to the box or does that have to be steel from the ground up?

Thanks
Mark

[BruceM]

That's a nice box with receptacle.   PVC conduit into the outside box is OK, you'll just need to add steel post in concrete to support the box.  You'll have a first class hookup!

[buickanddeere]

  The concept is to avoid paralleling the ground path and neutral current path.
   Those people who think ground and neutral are the 'same" are missing some crucial info.
     The ground system is supposed to hold metal enclosures and the neutral conductor at the first 'service" to near earth potential. Little to no current unless there is a fault from line to ground.
       The neutral system is designed to carry working load current.
         The ground wire is usually bare or green and the neutral is insulated and white for a reason.